Variations in Mesopause Region Characteristics: Space-Factor Effects

Some important data on both lunar tidal and solar effects on mesopause region characteristics, which were obtained by scientists of the Obukhov Institute of Atmospheric Physics in cooperation with colleagues from other organizations, are discussed. The present-day evidence that supports the hypothesis proposed by A.I. Semenov and N.N. Shefov about the existence of oscillations (with periods of the lunar synodic month and its half) in the mesopause region characteristics is considered. The oscillation amplitudes are estimated based on a statistical analysis of measurement data, possible mechanisms for generating these oscillations are indicated. Statistical data on the effect of solar activity on the mesopause region are discussed. It is shown that the effects of solar activity on some atmospheric characteristics on interannual and intraseasonal time scales have opposite signs, which suggests that there are different physical mechanisms of solar-terrestrial relations within these frequency ranges.